Inghouse electric



Dec. 6, 1927.

C. LE G. FORTESCUE TRANSMISSION SYSTEM Filed July 3l, 1924 WITESSES: /62 j Piu/MW INVENTOR lll Patented Dec. tif, 192?.

CHARLES LE G. FORTESCUE, OF PITTSBURGH, PENNSYLVANA, ASSIGNO T WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

TRANSMISSION SYSTEM.

Application led July 3l, 1924.

My invention relates to electrical power transmission lines or systems and regulating apparatus therefor, and particularly to systems for the transmission of power at high voltages over long distances.

In a copending application of crank G. Baum, Serial No. 569,704, tiled June 20, 1922, patented February 8, 1927, No. 1,617,007, is shown a system that is particularly adapted to the high-voltage, long-distance transmission of electrical power, this system embodying a plurality of synchronous condensers spaced along the line at remote intervals and adapted to provide the wattless current required in each section of the line between condenser stations, whereby a substantially constant voltage may be maintained throughout a relatively long transmission line.

One object of my invention is to provide. in conjunction with a system of the aboveindicated character, means .for maintaining a substantially constant voltage upon load circuits at the respective condenser stations, while inherently holding the main transmission line voltage to a practically constant value, or one thatslightly rises with increasing load.

More specifically stated, it is an object of my invention to provide, in conjunction with a transmission line and a three-winding transformer that is energized therefrom, a synchronous condenser that is connected to one of the secondary windings, together with a regulator that is adapted to adjust the field excitation of the synchronous condenser in accordance with the voltage across the other secondary transformer winding, to which the load circuit is connected.

Other objects of mv invention will become evident from the following detailed description taken in conjunction with the accompanving drawing, wherein Figure 1 is a diagrammatic view of a transmission and distribution system organized in accordance with my present invention;

Fig. 2 is an equivalent branch circuit impedance diagram serving to illustrate the relative impedance values introduced into certain parts of the system illustrated in Serial No. 729,245.

F l by the circuits of the transformer; all

Fig. 3 and Fig. 4 are vector diagrams illustrating certain relations of various electrical quantities that are present during the operation of the illustrated system.

Referring to Fig. 1, the system here shown comprises a transmission line embodying conductors 1 and 2, to which one or more generators 3 are connected through suitable step-up transformers 4, the generators being regulated for constant voltage by means of an exciter 5 and a suitable regulator as illustrated.

it will be appreciated that, in actual practice, the transmission system will be of the three-phase type although, for the sake of simplicity, a single-phase system has been illustrated.

At intervals along the transmission line, a plurality of condenser substations, such as 6, 16 and 26, are provided for the purpose of maintaining a substantially constant voltage upon the transmission line and effecting the transmission of relatively large blocks of power over the line, as more fully set forth in the above-identified application of Frank (l. Baum.

- Each condenser station comprises a synchronous condenser' 7, an exciter 8 therefor, a broad-range regulator 9, and a suitable step-down transformer having a primary winding l0 and a plurality of secondary windings 11 and 12, the winding 11 being connected to the primary or stator winding 14 of the synchronous condenser 7, while the winding 12 is connected to a load circuit 13.

The exciter 8, which may be of any suitable character, is adapted to energize the field winding 15 of the synchronous condenser, While a plurality ofresistors 17 and 18 are provided in conjunction with the broad-range regulator 9 to automatically adjust the field excitation of the condenser.y The main voltage coil of the regulator 9 is connected across the secondary transformer winding` 12, as indicated; thatis to say, across the load circuit 13, whereby the synchronous condenser field excitation is regulated in accordance with the voltage of the transformer winding 12, or in other words, a substantially constant voltage is maintained upon the load circuit 13 by means of the illustrated interconnections of the regulator 9 with the synchronous condenser field winding 1,5 and the load circuit 13.

inasmuch as the particular type of regulator to be employed is not relevant to the present invention, Since any suitable-regulator for automatically over-exciting and under-exciting the field winding 15, as desired, may be employed, I have not deemed it necessary to illustrate the details of such a regulator. As examples thereof, reference may be had to xTirrill Patent No. 1,192,708, which was 'granted July 25, 1916 and to a copending application of H. A. 'l`ravers,'reg ulator fsystem's Serial No. 540,178, filed March 1, 1922r and assigned to the Westinghouse Electrica`Manufacturing Company.

By means of Athe illustrated systeln, a substantially constant voltage is maintained upon the load circuit where a steady voltage is very desirable, particularly in the case of lighting loads, 'while a practically constant voltage or one slightly rising with increasing loadmay be maintained uponthc transmission line 1, 2, as more fully hereinafter explained.

Referring to Fig. 2, the impedances Zw, Z11 and 2,2, which respectively correspond to the Stepdowntransformer windings 10, 11 and 12'sh0uld be's'o chosen,`following well-known principles of transformer design, that the effect of the Aload currents produced by the synchronous condenser 7 inthe winding 11 will substantially annui the voltage rise caused by the resistance load, or other load oper-ating'at any power-factor other than unity, 'on the secondary transformer winding 12. This relation of impedances of the various portions of the circuit'will afford the best conditions for achieving the objects of the present invention. Y y

Avectorial diseussioirof the circuit conditions is given below with reference to Fig. 3 and Fig. Ltof the drawing. In-this discussion, vthe various quantities,^suchA as voltages, currents andresistances, are`considered on the basis of a 1 to 1 ratio of transformation, for the sake of simplicity.

'Let Xab represent thetotal leakage reacta-nce between the primary winding 10 and the secondary Winding 11;

VXalc represent the total 'leakage reactance between the primary winding 10 land the other Vsecondary winding 12 ,and

Xbcrepresentthe tota-l leakage reaetance between the Isecondary winding -11 and the other secondary Winding-12.

`Consider first the special case correspond ding to the above discussion of 2, "wherein Xab+XaCV-Xbcr=(). It m-ay beishown that 1,/2 (XM, -l--Xac-*XEJ is equal tothe effective impedance Zu, of the equivalent diagram of Fig. 2, (neglecting the relatively small resistances of the transformer windings). Thus, if Z10 is substantially zero, the voltage at the terminal of Z1, is not affected by any load that may be drawn from Zu, and vice versa.

As illustrated in Fig. 3, El, and El, correspond to the voltages of the secondary windings 11 and 12. respectively, and willv be substantially in phase. Consequently, `for a unity-power-factor load 13 on 'the winding 12, the corresponding currents I11 and 1,2 will be substantially in quadrature. he resistances ofthe windings 10, 11 and 12, respectively, are-represented by the characters R10, R11 and'Rlg. It will thus-be noted that the voltage drop (R10 1,1) is substantially in quadrature with the voltage E12 of the secondary winding 12. Since'. this secondary winding is regulatedfor constant voltage, it follows that-E10, the terminal 'voltage'of the primary winding "10, will rise slightlyV with load. However, this rise willbe on the order of about one per cent and thus,'by regulating for constant voltage'on` theload circuit (13 in Fig. 1) ,theprimary voltage, that is the voltage of the transmission line proper, is held at a practically constant or slightly rising value by the Vinherent action of the three-winding transformer and the) illustrated regulating systemtherefor.

Moreover, if desired the variation of the primary or line voltage' from the normal may be decreased still further-by an-approp'riate selection Aof the value of (Xab,+Xac-Xbc) slightly different from the zero value assumed above. The diagram of Fig. 4 shows the impedance drops when'this value is rela tively small and thecurrent L, leads the current 1,2. p

As will be noted from the diagram, at full load a transformer connected-to .the end of the transmission line would take 2a leading current corresponding to the value' of In and a load currentpcorresponding to the Value of 1,2. Under the conditionsassumed, the primary or line voltage would be Fim. Under 11o-load conditions, when 1,2 equals zero, the transmission line requires a lagging current such as I. In' this event,'the. primary voltage may berepresented by Em;

Consequently', by an appropriate choice of the inductanee vvalues Xab, etc., the scalar values of the voltages Em and El, atfull load and 'at no load, respectively, could be made substantiallyequal.

Forintermediate values of load..Y the primary veltagewouldl vary an insignificant amount from the' valuesffat lno load aindfull load. Under the conditions last assumed, therefore, the voltage on ther load circuit is maintained constant and,at the same time, the primary or line voltage is also main tained practically Without variation.

It will be understood that the transformer 6 should be designed and proportioned with due regard to the power-factor of the load to be carried. Vhere this power-factor fluctuates to any extent, there Will be a tendency towards fluctuation in the primary voltage. However, the primary voltage may he maintained substantially independent of such fluctuations by proper design of the transformer itself `,I do not-wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be made without departing from the spirit and scope of my invention. I desi re, therefore. that only such limitations shall be imposed as are indicated in the appended claims.

AI claim as my invention:

1. In a system of transmission, the combination with a transmission line, of a plural-secondary-Winding transformer energizedtherefrom, a load circuit and a dynamo-electric machine connected to different windings of said transformer, and means for regulating the excitation of-said machine 1n accordance with the voltage of said load circuit.

2. In a system of transmission, the combination with a transmission line, of a plural-winding transformer energized therefrom, a load circuit and a dynamo-electric machine connected to different secondary windings of said transformer, and means for regulating the excitation of said machine in accordance with the voltage of said load circuit.

3. In a system of transmission, the combination with a transmission line, of a plural-secondary-winding transformer energized therefrom, a load circuit and a dynamo-electric machine connected to di'erent windings of said transformer, and means for maintaining a substantially constant line voltage, Said means comprising a regulator controlled in accordance with the voltage of said load circuit for adjusting the excitation of said machine.

4. In a system of transmission, the combination with a transmission line, of a pluralwindingr transformer energized therefrom, a load circuit and a dynamo-electric machine connected to different secondary windings of said transformer, and means for maintaining a substantially constant line voltage, said means comprising a regulator controlled in accordance with the voltage of said load circuit for adjusting the excitation of said machine.

5. In a system of transmission, the combination with a transmission linev` of a pluralwindingr transformer energized therefrom, a dynamo-electric machine connected to a secondary winding of said transformer. and means for regulating the excitation of said machine in accordance with the voltage of another former. i

6. In a system of transmission, the combination with a transmission line, of a pluralsecondary-winding transformer energized therefrom, a dynamo-electric machine connected to one winding of said transformer, and means for maintaining a substantially constant line voltage, said means comprising a regulator controlled in accordance with the voltage of another winding of the transformer for adjusting the excitation of said machine. Y

7. In a. system of transmission, the combination with a transmission line, of a pluralwinding' transformer energized there-from, a dynamo-electric machine connected to a secondary winding of said transformer, and means for maintaining a substantially con- .etant line voltage, said means` comprising a secondary winding of the transregulator controlled in accordance with the voltage of another secondary vWinding of the transformer for adjusting the excitationl of said machlne. i

8. In a system of transmission,;the,combi- I' nation with a transmission line, of a pluralwinding transformer energized therefrom, a load circuit and a synchronous condenser connected to different secondary windings of said transformer, and means for regulating the field-winding current of said synchronous condenser in accordance with the voltage of said load circuit.

9. In a system of transmission, the combination with a transmission line, of a pluralsecondary-winding transformer energized therefrom, a load circuit and a synchronous condenser connected to different windings of said transformer, and means for-maintaining a substantially constant line voltage, said means comprising a regulator controlled in accordance with the voltage of said load circuit for adjusting the field winding current of said synchronous condenser.

l0. In a system of transmission, the combination with a transmission line` of a plural-winding transformer energized therefrom, a load circuit and a synchronous condenser connected to different secondary windings of said transformer, and means for maintaining a substantially constant line. voltage` said means comprising a regulator controlled in accordance with the voltage of said load circuit for adjusting the field winding current of said synchronous condenser.

ll. A transmission system comprising a source of power, a synchronous condenser, a load, a transformer having three windings, the primary winding being connected to said source, another winding to said condenser and the third to said. load, a regulator energized in accordance with the load voltage for governing the excitation of said condenser and maintaining a substantially constant. load voltage, said transformer being lll) further ndnpted to maintain substantially constant voltage across its Primmv winding.

12. The combination with n three-winding transformer, of a l'oad cil-Cuit connected 'ro one winding. a `device drawingY variable reactive Current-components connected to a second winding, and means responsive. tothe voltage'of sui'd 'load circuit 'for cont-rolling said reactive current-components in the second Winding, whereby tl'esired'voltnie conditions may be maintained on said load circuit,-t,he effective -r'eactnce impedance between the said first and second windings being approximately equal to the sum 'of the effect-ive reactaince inipedanee between the 'third vindingwmd Said first winding plus the 'effective 'renctzlnce impedance between the said third windingA :intl the sniil second winding. whereby the voltages :it thelerniinais ofthe'said lirst and second windings are substantially in phase and independent ol thelload conditions of the :respective windings. y

13. The combination with a vthree-Winding transformer, of a'load circuit connected lo one' Winding, l-a variableareactancedevice connected tn :i second-Winding, 4:incl 1nenns responsive-to the A`voltage of estiitl load circuit 'for controlling said rreative"current-coin- -pon'en'ts in 'xthe second winding', whereby'del'etl volt/age conditions may he maintained von :said lozid circuit, the=elective resistance -iinpetlance 4between the said first and second windings being very nearly` btrtwnot lquite, equal tioft-h'e's'u'rn of the. effectiverea-:ctance impedance 1 liet/Ween 'the "thind `winding and said irst Winding plusthe'etfective fretctance impedance flietween-itfhe lsa'id fthird Winding und Vthe said -second winding, Whereby'the voltages at-the telminals 0f-the saidtirstlzind eccomi ltri-z'itlingsaresubstmitinlly in lphase :ind independent of the l'oa'riforitlibions 'oftfliic respective windings, ant'lvhereby the volt- :iffe onlhe'thiitlfwinding-when a representative 'load-is drawn ifvom {the first win'dingQis subst'ntfictlly- 'e'q'ualvto lthe'votage'n the 1 hird Winding' during-em loa-dconditions.

- :In )testimony whereof; hzwe rhereuintosub- 

